This invention relates to catalytic compositions and their use for the hydroprocessing, e.g. hydrodesulfurization and hydrodemetalation of feedstocks containing sulfur and metals. In particular, this invention concerns shaped extruded catalysts that are polylobal in cross-section.
A number of catalyst shapes have been described in the prior art. U.S. Pat. No. 2,408,164 to Foster discloses catalyst shapes including solid and hollow cylinders, elongated star shapes, cylinders with corrugated edges, etc. Similar shapes are also shown in U.S. Pat. No. 3,997,426 to Montagna et al. U.S. Pat. Nos. 3,966,644 and RE. 30,155 issued to Gustafson disclose trilobal catalysts for hydrocarbon conversion. U.S. Pat. Nos. 3,674,680 and 3,764,565 to Hoekstra and Jacobs disclose catalyst shapes designed to eliminate catalytic material more than 0.015 inch from the catalyst surface and give surface area to volume ratios of between 100 and 250 inch.sup.-1. U.S. Pat. No. 3,347,798 to Baer et al discloses the production of hollow bead catalysts. U.S. Pat. No. 3,957,627 discloses spherical catalysts having a void center and a hole extending to the external surface. U.S. Pat. Nos. 4,116,819 and 4,133,777 disclose catalysts in the shape of elongated extrudates having alternating longitudinal grooves and protrusions on the surface.
The purpose of shaped catalysts has been to increase surface-to-volume ratio over conventional shapes, such as round cylinders and spheres to increase effective diffusion and increase metals loadings. Surface-to-volume ratios can be increased by reducing the size of the particles, but beds of such particles tend to have unacceptably high pressure drops across the bed.